Tin-containing thioxanthate compounds and lubricants containing them



TIN-CONTAINING THIOXANTHATE COMPOUNDS AND LUBRICANTS CONTAINING THEM John P. McDermott, Springfield, N. 1., assignor to Fsso Research and Engineering Company, a corporation of Delaware No Drawing. A plication September 21 1953 seinr No. 381,513

15 Claims. (Cl. 252-336) The present invention relates to a new class of tincontaining compounds and more particularly to the use of these compounds as additives for various hydrocarbon products. This is a continuation-in-part of Serial No. 256,597 filed November 15, 1951 now abandoned.

In the development of marketable hydrocarbon prodacts such as lubricating oils, the trend has been to use more and more efiicient refining methods in order to improve their stability and reduce their tendency to form carbon and deposits of solid matter or sludge. While such highly refined materials possess many advantages, their resistance to oxidation, particularly under conditions of severe service, is generally decreased and they are more prone to form soluble acid oxidation products which are corrosive. They are generally less effective than the untreated products in protecting the metal surfaces which they contact against rusting and corrosion due to oxygen and moisture. Such lubricants also often deposit thick films of varnish on hot metal surfaces, such as the pistons of internal combustion engines.

In accordance with the present invention a new class of chemical compounds has been discovered, and these compounds have been found to reduce the tendency of refined lubricating oils and other hydrocarbon products to coil-ode metal surfaces when added in small quantities to suchhraterials. These additives are active in reducing the corrosion of copper-lead and cadmium-silver bearings which are employed in internal combustion engines, they are likewise effective in inhibiting the oxidation of hydrocarbon products generally and especially those of petroleum origin, and they impart other useful properties to various products.

The new class of compounds forming the subject of the present invention are tetravalent tin compounds having four organo radicals comprising at least two oil solubilizing hydrocarbon radicals attached directly to the tin through carbon atoms and having at least one thioxanthate radical attached directly to the tin through a sulfur atom. The compounds are conveniently formed by reacting an organo tetravalent tin halide with a salt of a thioxanthic acid in such manner that halogen in the tin compound is substantially completely replaced by the organic radical. The compounds are stable and soluble in the usual hydrocarbon products such as fuels, lubricating oils and the like, are good anti-corrosive agents for organic materials that tend to corrode the usual metals, and have other useful properties.

The new class of compounds of the present invention may be more accurately defined by the following general formula:

wherein R is a hydrocarbon radical, w is 2 to 3, y is l to 2 and w plus y totals 4. R is also a hydrocarbon radical. R and R each preferably have 1 to 20 carbon atoms and may be alkyl, alkenyl, cyclo-alkyl, aryl, aralkyl, and alkaryl radicals. Alkyl radicals such as methyl, isopropyl,

United States Patent Patented Ma. 26, 19s:

formula:

( h qih wherein R is a hydrocarbon radical as defined above, X is a reactive halogen such as chlorine, bromine and iodine, wis2to3,yis l to2andwplusytotals4. Specific compounds include dibutyltindichloride, triphe'nyl tiniodide, tri-tert.-octyl tini odide tri-cyclohexyltinchloride, di-n-hexyltindibromide and the like. The halide preferably has two R radicals, and the R radicals are preferably alkyl radicals. The organo tetravalent halides may be prepared by means well known to the art.

The salts of thioxanthic acids are represented by the following Formula 1:

S R S-PJ-SY Thloxnuthate R has the meaning defined abdve. Y is a cation and is preferably a metal equivalent of hydrogen. The reactive alkali and alkaline earth metals such as sodium, potassium, calcium and the like may be Ammonium or amine salts may also be used. The thioxanthates may be prepared by well-known means.

Specific salts of the above general types include potassium, sodium, lithium, barium, ammonium and the like salts of ethyl thioxanthic acid, isoamyl thioxanthic acid, n butyl thioxanthic acid, hexadecyl thioxanthic acid, ethylcyclohexyl thioxanthic acid, n-nonyl thioxanthic acid, benzylthioxanthic acid, isopropyl' ethyl thioxanthic acid, didodecyl thioxanthic acid, Lorol-B thioxanthic acid (where Lorol-B compounds are derived from Lorol- B" alcohol which is a commercial mixture of higher alcohols commonly dcrived from cocoisut oil and having from 8 to '18 carbon atoms per molecule), and the like.

The particular compound selec ed will depend largely on the concentrations used and 1e specific properties to be improved in various hydrocarbon products. 'lhioxanthate derivatives are not only anti-oxidants but may be used in cutting oils where high sulfur concentrations are desired and as extreme pressure I, lives for other uses.

Suflicient salt of the acid is reated with the tin halide compound to replace the halogen substantially completely. A typical reaction is represented by. the following fonnula:

Thus from 1 to 2 mols of the desired thioxanthate radical will be used for tin compounds having from 1 to 2 atoms of halogen although it may be desired to use excess salt in order to insure complete reaction. In carrying out the reactiomthe salt may be added relatively slowly to the tin halide with care being taken to prevent excessive temperature rise as a result of the exothermic reaction which takes place. The reactants may be heated together for a period of from about 0.5' to 2 hours, dc pending on the types of materials present. Preferably, the reaction temperatures are maintained in a range of about 10 to C. Conveniently, the reaction is carried out in the presence of an inert solvent in which the halide reaction by-product's are insoluble or from which such by-products may be readily removed. Such solvents include petroleum ether, methyl alcohol, ethyl alcohol, isopropyl alcohol, acetone, dioxane and the like. The heating step may be carried out under refluxing conditions when a solvent is used. The resulting metal halide will generally precipitate out of solution and may be removed by filtration, decantation or by other means. Solvent may be removed from the finished product by stripping with nitrogen or other inert gas, by distillation or by other means. A desired method for producing a relatively pure product is to filter the material, preferably before solvent is removed, through a diatomaceous filter aid such as Hy-flo.

If the products of the present invention are added to a mineral oil for inhibiting oxidation and preventing corrosion of metal parts and the like, they are preferably used in proportions of about 0.01 to or by weight based on the total composition. A preferred range is from about 0.1 to 2% by weight. Concentrations up to as high as or even higher may be used for extreme pressure lubricants, cutting oils, and the like. It is usually preferred, when marketing the additive commercially and especially when intended for use in lubricating oils, to prepare a concentrated lubricating oil solution in which the amount of additive in the composition ranges from about 20 to 50% or up to 75% by weight, depending on the solubility of the additive in the oil. The concentrate is then conveniently transported and stored in such form and may be subsequently blended with a base lubricant in the required amount before being used as a crank case oil or the like.

The invention will be more fully understood by reference to the following examples. It is pointed out, however, that the examples are given for the purpose of illustration only and are not to be construed as limiting the scope of the present invention in any way.

EXAMPLE I.-PREPARATION OF PRODUCTS Product A.TriphenylrinlaI/rylthioxnnthate To a stirred solution of 19.0 g. (0.04 mol) of triphenyltiniodide in 300 ml. of acetone was added a solution of 12.6 g. (0.04 mol.) of potassium lauryl thioxanthate in 200 ml. of methanol over a period of one hour with rapid stirring, during which time the reaction mixture turned turbid. The entire reaction mixture was then placed on the steam bath to remove the solvent. The product was filtered to remove the crystalline potassium iodide, whereupon a yellow viscous oil was obtained which analyzed 16.1% Sand 17.7% Sn.

EXAMPLE II Laboratory bearing corrosion test A blend was prepared containing 0.25% by weight of the product prepared as described in Example I using as the base oil a solvent extracted, paraifinic type mineral lubricating oil of S. A. E. ---20 viscosity grade. Samples of these blends and a sample of the unblended base oil were submitted to a laboratory test designed to measure the effectiveness of the additive in inhibiting the corrosiveness of a typical mineral lubricating oil towards the surfaces of copper-lead bearings. The test was carried out substantially as described in Example 12 of U. S. Patent No. 2,529,303 to McDermott. The results are reported in the table below as Bearing Corrosion Life which shows the number of hours required for the hearings to lose 100 mg. in weight determined from data obtained in the test.

The additives of the present invention may be used in various lubricating oil base stocks derived from petroleum distillates and residuals refined by conventional means. Hydrogenated oils or white oils may be employed as well as synthetic oils prepared by polymerization of olefins, by reaction of oxides of carbon with hydrogen, or by hydrogenation of coal. The products may also be used in the synthetic polyether and polyester-type lubricants and the like as such or blended with mineral lubricants. The lubricants will usually range from about to 150 seconds (Saybolt) viscosity at 210 F.

Other agents may of course be employed in the oil compositions, such agents including dyes, pour point depressants, sludge dispersers, thickeners, viscosity index improvers, oiliness agents, and the like. In addition to being employed in lubricants, the additives of the present invention may also be used in other mineral oil products such as motor fuels, heating oils, hydraulic fluids, cutting oils, turbine oils, transformer oils, gear lubricants, greases and other products containing mineral oils as ingredients. What is claimed is: l. A hydrocarbon product having incorporated therein in the range of about 0.01 to 20% by weight of an organotetra-valent tin compound of the formula:

wherein w is 2 to 3, y is l to 2, w plus y totals 4, and R and R represent hydrocarbon radicals having 1 to 20 carbon atoms.

2. A composition as in claim 1 wherein said hydrocarbon product is a mineral lubricating oil.

3. A composition as in claim 1 in which R is an alkyl radical.

4. A composition as in claim 1 wherein R is a phenyl radical.

5. A lubricating oil composition comprising a major proportion of a mineral lubricating oil and in the range of 0.1 to 2% by weight, based on the total composition of triphenyltinlaurylthioxanthate.

6. A concentrate consisting essentially of a mineral lubricating oil and the tin compound of claim 1, said compound being present in an amount equal to about 20 to 50% by weight of said concentrate.

7. As a new composition of matter an organo-tetravalent tin compound of the formula wherein R is a hydrocarbon radical having 1 to 20 carbon atoms, w is 2 to 3, X is a reactive halogen, y is 1 to 2, and w plus y is 4, with a salt of the formula wherein Y is a cation selected from the group consisting of alkali metals, alkaline earth metals and ammonium radicals and R is a hydrocarbon radical having 1 to 20 carbon atoms, suflicient of said salt being used to substantially completely replace halogen in said tin halide, and removing halide reaction products therefrom.

12. The process according to claim 11 wherein said reaction is carried out in the presence of a substantially inert solvent.

13. The process according to claim 11 wherein Y is an alkali metal.

14. The process according to claim 11 wherein said compounds are heated together at a temperature in the range of about 10 to 100 C.

15. As a new composition of matter an organo-tetravalent tin compound of the formula s (B) sna -s11)- wherein w is 2 to 3, y is 1 to 2, w plus y totals 4, R represents an aryl'radical having 6 to 20 carbon atoms and R represents an alkyl radical having 1 to 20 carbon atoms.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Gillman: Organo Tin Compounds, 0. S. R. D. 548, Serial No. 236, May 2, 1942, page 12. 

1. A HYDROCARBON PRODUCT HAVING INCORPORATED THEREIN IN THE RANGE OF ABOUT 0.01 TO 20% BY WEIGHT OF AN ORGANOTETRA-VALENT TIN COMPOUND OF THE FORMULA: 